Abstract: A procedure specifically for the execution of a diagnosis of an emission treatment system is being introduced. The pressure of the reagent between the first and second valve and/or between the second valve and the injector valve is measured and the pressure measuring signal are the basis of the diagnosis. The first and second valve, are opened in an alternating cycle, where the opening time, and/or the period duration of the first and second valves are set in such a way that the emerging diagnostic flow volume is smaller than the measuring flow volume. The procedures pursuant to the invention thereby reduce the influence of dynamic precursors of the reagent flow in the reagent line and enables, aside from an increase in reliability of the diagnosis results, a diagnosis possibility of small leakages.

Abstract: A procedure specifically for the execution of a diagnosis of an emission treatment system is being introduced. The pressure of the reagent between the first and second valve and/or between the second valve and the injector valve is measured and the pressure measuring signal are the basis of the diagnosis. The first and second valve, are opened in an alternating cycle, where the opening time, and/or the period duration of the first and second valves are set in such a way that the emerging diagnostic flow volume is smaller than the measuring flow volume. The procedures pursuant to the invention thereby reduce the influence of dynamic precursors of the reagent flow in the reagent line and enables, aside from an increase in reliability of the diagnosis results, a diagnosis possibility of small leakages.

Abstract: A procedure for the pressure diagnosis in a reagent substance metering system, which introduces a reagent substance into an exhaust gas area of an internal combustion engine upstream in front of at least one exhaust treatment device as well as a device to implement the procedure is proposed. The reagent substance pressure occurring between a metering valve and a security valve disposed downstream after the metering valve is measured during different operating conditions of the metering valve and/or the security valve and is compared with at least one threshold value. An error signal is provided when the threshold is exceeded. The procedural approach according to the invention allows for a leakage diagnosis of the reagent substance metering system. Furthermore, the procedural approach according to the invention allows for a diagnosis of metering valve and/or the security valve and/or the check valve.